1. Field of the Invention
The present invention relates to a protective circuit assemblage for a multi-voltage electrical system, for example in a motor vehicle, in order to exercise control over internal and optionally external faults, in particular short circuits and polarity reversals. The protective circuit assemblage can be both at least in part a constituent of a DC voltage converter, and provided separately in the multi-voltage electrical system.
2. Description of the Related Art
DC voltage converters are used to convert different voltages. “DC voltage converter” usually refers to an electrical circuit or electrical component that converts a DC voltage delivered at the input into a different DC voltage.
DC voltage converters are utilized, for example, in so-called “multi-voltage” electrical systems, in which an input voltage that is primary-side in terms of the converter is converted into a comparatively high or low secondary-side output voltage. The term “multi-voltage electrical system” refers to electrical networks having multiple loops that are operated with different electrical voltages. In the context of interaction of the different loops, it is necessary to convert the electrical voltage between them.
Multi-voltage electrical systems are used in motor vehicles as electrical power supply systems that, in addition to low-voltage loads that are usually set to a DC voltage of 12 V, also work with at least one high-power load set e.g. to 48 V. The multi-voltage electrical system has for this purpose a corresponding high-power generator and/or a corresponding high-power battery, as well as a DC voltage converter that converts the DC voltage of, for example, 48 V into a 12 V voltage at approximately the same power level. Typically the multi-voltage electrical system of a motor vehicle usually also has a low-voltage battery, for example a 12 V battery.
DC voltage converters are used in motor vehicles, for example, in a low-voltage hybrid system. In this application, the DC voltage converter transfers energy between the 48 V and 12 V vehicle electrical systems. The 48 V vehicle electrical system represents a high-voltage loop, and the 12 V vehicle electrical system represents a low-voltage loop. A DC voltage converter of this kind is referred to as a “power conversion unit for boost recuperation system” (PCU-BRS).
One challenge to this converter is that of protecting the 12 V vehicle electrical system. This must be ensured even in the event of a short circuit from the high-voltage side to ground, and failure of the half bridges.
It is known to provide a breaker, for example a semiconductor switch, on the 12 V side for such a protective circuit.
The published German patent application document DE 10 2008 041 341 A1 discloses a DC voltage converter that is utilized in an electrical system of a motor vehicle. In the DC voltage converter described, the external ground potential is separated from an internal ground potential node when the DC voltage converter is in the switched-off state. Parasitic current flows are thereby largely avoided.